Sadly I reckon the police, on talking to those closest to Nicola from the beginning, maybe suspected there was another more sinister scenario which is why they were so adamant from very early in in the investigation that they did not suspect a 3rd party or a 'crime' was involved despite there no signs of her falling into the river.
Of course they have had to search the river as she may well be in there anyway.
Her partner didn't seem to have any family members supporting him during his interview with the press. Maybe they were in the background, off camera? No emotion or appeal for her to get in touch if she's still out there either. He wasn't part of the family appeal with Nicola's family.
Not casting aspersions of course just all very odd. The police are making themselves look like bumbling plods for a reason I think,